Class AbstractFuture

output/java_guava/1.4.18/AbstractFuture.java:61–1084

An abstract implementation of ListenableFuture, intended for advanced users only. More common ways to create a ListenableFuture include instantiating a SettableFuture, submitting a task to a ListeningExecutorService, and deriving a Future from an existing one,

@GwtCompatible(emulated = true)
public abstract class AbstractFuture<V> implements ListenableFuture<V> {
  // NOTE: Whenever both tests are cheap and functional, it's faster to use &, | instead of &&, ||
  private static final boolean GENERATE_CANCELLATION_CAUSES = Boolean.parseBoolean(System.getProperty("guava.concurrent.generate_cancellation_cause", "false"));

  /**
   * A less abstract subclass of AbstractFuture. This can be used to optimize setFuture by ensuring
   * that {@link #get} calls exactly the implementation of {@link AbstractFuture#get}.
   */

  abstract static class TrustedFuture<V> extends AbstractFuture<V> {
    // N.B. cancel is not overridden to be final, because many future utilities need to override
    // cancel in order to propagate cancellation to other futures.
    // TODO(lukes): with maybePropagateCancellation this is no longer really true. Track down the
    // final few cases and eliminate their overrides of cancel()
    @CanIgnoreReturnValue
    @Override
    public final V get() throws InterruptedException, ExecutionException {
      return super.get();
    }

    @CanIgnoreReturnValue
    @Override
    public final V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
      return super.get(timeout, unit);
    }

    @Override
    public final boolean isDone() {
      return super.isDone();
    }

    @Override
    public final boolean isCancelled() {
      return super.isCancelled();
    }

    @Override
    public final void addListener(Runnable listener, Executor executor) {
      super.addListener(listener, executor);
    }
  }

  // Logger to log exceptions caught when running listeners.

  private static final Logger log = Logger.getLogger(AbstractFuture.class.getName());

  // A heuristic for timed gets. If the remaining timeout is less than this, spin instead of
  // blocking. This value is what AbstractQueuedSynchronizer uses.
  private static final long SPIN_THRESHOLD_NANOS = 1000L;
  private static final AtomicHelper ATOMIC_HELPER;

  static {
    AtomicHelper helper;
    try {
      helper = new UnsafeAtomicHelper();
    } catch (Throwable unsafeFailure) {
      // catch absolutely everything and fall through to our 'SafeAtomicHelper'